Method and set of instructions for the dosed supply of printing instructions to a printer, and system for practicing the method

ABSTRACT

In the printing and finishing of sheet-like objects, printing instructions are outputted to a printer ( 2 ). In accordance therewith, sheet-like objects are printed by the printer ( 2 ). The objects are subsequently delivered by the printer ( 2 ) directly to the finishing apparatus ( 1 ) and then finished by the finishing apparatus ( 1 ). Output data concerning the printing instructions sent to the printer ( 2 ) which are at least indicative of the printer capacity required for the printer ( 2 ) to process the printing instructions outputted to the printer ( 2 ) are registered. Sheet-like objects displaced by the printer ( 2 ) are detected and signaled by the detector ( 12, 13, 27, 28 ). At least periodically, production data in accordance with the signals received from the detector ( 12, 13, 27, 28 ) are generated. These production data are at least indicative of a quantity of production realized by the printer ( 2 ) in response to the printing instructions sent to the printer ( 2 ). Depending on the production data, the output of next ones of the printing instructions to the printer ( 2 ) is dosed.

FIELD AND BACKGROUND OF THE INVENTION

[0001] This invention relates to a method according to the introductorypart of claim 1, to a system according to the introductory part of claim22 for practicing such method using a data processor system, and to aset of instructions for use therein.

[0002] Such a system and such a method are known from U.S. Pat.5,283,752. When in-line printing and finishing sheet-like objects—suchas in-line printing, combining with inserts, folding, inserting andfranking documents within the framework of composing postalitems—failures sometimes occur in the finishing process downstream ofthe printer.

[0003] In order to prevent accumulation of printed objects at the outputof the printer, it is then useful to stop the supply of printinginstructions to the printer. It is a problem here that modern printerscontain a considerable memory, in which, in operation, a buffer stock ofprinting instructions is stored, which printing instructions areprocessed on demand and with some delay after having been outputted tothe printer. If in response to a failure in the equipment for finishingprinted objects the supply of printing instructions has beeninterrupted, a number of sheet-like objects will still be printed inaccordance with printing instructions from the buffer stock.

[0004] Stopping the printing with a delay leads to paper waste. Objectsprinted during run-out of the printer and which could not be processedas a result of the failure must generally be removed by hand. Further,objects still printed and delivered after the occurrence of a failure(and before restart of the finishing apparatus) can run up onto thestationary, preceding objects. A potentially large number of objectsstill printed and delivered after the finishing apparatus has beenstopped further makes it difficult to determine the printinginstructions that are to be fed first to the printer at restart. Even ifa buffer is provided (such as a first-in-first-out buffer for individualreception and delivery of objects as described in European patentapplication 0 927 693) for intermediate storage of objects between theprinter and the apparatus for finishing the printed objects, it isdisadvantageous if the number of objects still printed after a failurehas occurred and the supply of printing instructions to the printer hasaccordingly been stopped is very large, since in that case the buffermust have a correspondingly great capacity.

SUMMARY OF THE INVENTION

[0005] It is an object of the invention to limit the number of documentsthat is still printed after stopping the supply of printing instructionsto a printer with a buffer memory. It is a further object of theinvention, within the framework of the capacity of the system, torealize production rates as high as possible.

[0006] According to the invention, this object is achieved by carryingout the printing and finishing of sheet-like objects according to whatis laid down in claim 1. In addition, the invention provides a systemaccording to claim 22, with which, while using a conventional universalprogrammable data processor system, such a method can be practiced, anda set of instructions according to claim 28 for programming such a dataprocessor system for use thereof within the framework of the proposedmethod.

[0007] The invention makes it possible to collect indications concerningthe influence of the dosing of printing instructions to the printer onthe productivity of the printer and, in accordance therewith, to choosethe dosing such that, on the one hand, the amount of instructions in thememory of the printer is limited and, on the other hand, theproductivity of the printer or at least of the combination of printerand finishing facilities is limited only slightly, if at all. Due to thedosing being controlled exclusively on the basis of parameters to beobserved outside the printer, no intervention or adaptation to specifictypes of printers is required and the proposed method can be applied toa great variety of printers without extensive adaptation. Sometimes,however, it may be useful to set the dosing depending on the situation,for instance on the basis of empirical data and depending on the type ofprinter and/or the type of printings.

[0008] Particularly advantageous elaborations of the invention are laiddown in the dependent claims. Further objects, practical aspects,advantages and details of the present invention will be describedhereinbelow with reference to the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a diagrammatic representation, in side view, of anexample of a system according to the invention,

[0010]FIG. 2 is a flow diagram of an example of a control for dosing thesupply of printing instructions to a printer,

[0011]FIG. 3 is a flow diagram of an example of a control forcontrolling a parameter of the control shown in FIG. 2, and

[0012]FIG. 4 is a flow diagram of a second example of a control fordosing the supply of printing instructions to a printer.

DETAILED DESCRIPTION

[0013] The exemplary arrangement shown in FIG. 1 comprises an apparatusfor finishing printed objects in the form of an inserter system 1 and aprinter 2. The printer 2 may be of a common commercially availableconventional type. According to the example shown, both the insertersystem 1 and the printer 2 are connected with a data processor system 3,in which data concerning the information to be printed on the documentsand concerning the associated finishing data are stored. However, theinvention may also be applied advantageously if the finishing is notcontrolled by the same computer as the printing The finishing may, forinstance, be controlled by another computer, directly or depending ondata scanned from the printed objects, for instance by scanning barcodes or characters. The finishing may also take place for all objectsof a series in the same manner, that is to say that on all objects of aseries the same operations are carried out. The instructions forprinting and finishing are, for instance, generated with the aid of aseparate computer system and converted in the data processor system 3 toadapted instructions for the printer 2 and, according to this example,for the inserter system 1. For the purpose of communication with sourceswhere data for, for instance, a mailing are generated, the dataprocessor system 3 is included in a network 46 as a printing andinserter server.

[0014] The inserter system 1 is built up from a control unit 4 and,coupled therewith, a first insert feeding station 6 (also referred to asinsert feeder) for feeding inserts, a conveying path 7, a second insertfeeding station 8, a folding station 9, an accumulating and conveyingstation 10 and an inserter station 11. The conveying path 7 extendsthrough the insert feeding stations 6 and 8 and through the foldingstation 9. The upstream end of the conveying path 7 forms a feedinginput 5 for feeding documents to be inserted to the inserter system 1and to the inserter station 11. According to this example the feedinginput 5 is arranged to receive one-by-one documents delivered by theprinter 2. It is also possible that the printer is arranged to groupobjects, such as a number of sheets of the same document, and candeliver them simultaneously as a stack, optionally bound or otherwisejoined together.

[0015] The second insert feeding station 8 is arranged to selectivelydeliver inserts directly to the folding station 9 or to the conveyingpath 7 extending under the folding station 9. Such an arrangement andconstruction of a second insert feeding station 8 and such anaccumulating and conveying station 10 are described in more detail inU.S. Pat. No. 5,561,963.

[0016] The inserter station 11 is provided with a detector 12 fordetecting the arrival of sets of sheets fed. The upstream end 5 of theconveying path 7 is provided with a detector 13 for detecting individualsheets, which, coming from the printer 2, reach the inserter system 1.

[0017] According to this example, the data processor system 3 and thecontrol unit 4 together form the control means for controlling theinserter system 1. It is also possible, however, to construct thecontrol means in a different manner. The inserter system 1 may, forinstance, be controllable by a control unit of its own. That own controlunit may, for instance, be formed by an associated standard computer,which controls the various functions of the inserter system via asuitable interface, or by a special, built-in control unit.

[0018] Located in the inserter station 11 is an inserting position 14,which is connected with the feeding input 5 through the conveying path 7and the accumulating and conveying station 10

[0019] The detectors 12, 13 are located between the feeding input 5 andthe inserting position 14, so that they can detect and signal thearrival of sheets, in the first instance moved by the printer, in twoplaces in the system. For that matter, detectors (not shown) that areconventionally arranged in the stations 6, 8, 9, 10, 11 or on theconveying path 10, may be provided as well, supplemental to thedetectors 12, 13 or instead of the detectors 12, 13. In that case, forinstance, the start of a finishing operation performed in response tothe arrival of a sheet of set of sheets may be used as an indicationthat a sheet of set of sheets has reached the respective station. Thisprovides the advantage that no separate detectors for detecting thearrival of a sheet of a set of sheets in the respective positions needto be provided.

[0020] The control unit 4 is arranged to count arrival signalsoriginating from the detectors 12, 13. Furthermore, the control unit 4is arranged to compare counted numbers of arrived documents or sets ofdocuments with reference numbers following from data stored in thecomputer concerning the printing and finishing of documents and togenerate an error message if the counted number of arrived documents orsets of documents and the associated reference number do not agree. Suchan error message may be a reason for stopping the inserter system 1.

[0021] The printer 2 is provided with two sheet trays A and B and anoutput 14 for delivering sheets to the feeding input 5 of the insertersystem 1. The conveying path 7 and the accumulating and conveyingstation 10 are provided with circulating conveyor belts 15, 16 providedwith conveying fingers 17, 18 for receiving and advancing documents andinserts on guide surfaces 19, 20 of the conveying path 7 and theaccumulating and conveying station 10. The inserter station 11 isprovided with an envelope hopper 21 for holding a stock of envelopes anddelivering one-by-one envelopes to be filled, a receiving holder 22 forreceiving filled envelopes and a discharge holder 23 for receiving itemsnot to be inserted and envelopes that should not (yet) be sealed up.

[0022] Located in the inserter station 11, downstream of the detectors12, 13, is a switch 44, to which is connected a branch 45, which, inturn, leads to the discharge holder 23. The control unit 4 is arrangedto operate the switch 44 for shunting documents in response to a signaloriginating from the detector 13. Thus the objects not to be inserted ornot to be sent immediately can be shunted to the deposition point 23.Consequently, these do not need be separated from the items destined foraddressees.

[0023] According to this example, the system according to the inventionis composed of the inserter system 1 for finishing sheet-like objectsprinted by the printer 2, a communication port 25 for connecting thedetector 12 and/or 13 of the inserter system to a data processor system3 for signaling to the data processor system detection by the detector12 and/or 13 of the sheet-like objects conveyed by the printer 2; and aset of instructions in a form readable and processable by the dataprocessor system 3. In combination with the printer 2 and the dataprocessor system 3, which may both be of any commercially available typeof one's choice, the examples of the proposed method described below maybe applied.

[0024] The inserter system 1 forms the apparatus for finishingsheet-like objects printed by the printer 2 and has an input 5 for eachtime receiving directly from the printer each of the sheet-like objectsprinted by the printer 2. The inserter system 1 is further arranged tofinish the sheet-like objects received from the printer 2 to obtainpackaged postal items. Both the detector 12 and the detector 13 may beused to detect sheet-like objects displaced by the printer 2. It is alsopossible to derive the number of printed sheets from other eventscoupled thereto, such as numbers of franking provided on postal items,if franking, too, is carried out in line with the printing.

[0025] In response to a failure in the finishing apparatus 1 downstreamof the printer 2, the sending of printing instruction sets to theprinter 2 is stopped. The printer 2, however, is then still printingsheets and delivers them until all the printing instruction sets sent tothe printer 2 have been processed to yield printed sheet-like objectsThe proposed measures ensure that, on the one hand, the number of sheetsstill printed and delivered after a failure in the inserter system 1 islimited and, on the other hand, the production rate of the printer 2, orat least the total system of printer 2 and inserter system 1, is limitedonly slightly, if at all, by a lack of printing instructions in thebuffer memory 26 of the printer 2.

[0026] According to this example, the set of instructions is formed by acomputer program, that is, software in a digital form which, whether ornot after compilation, is processable by the data processor system.

[0027] The set of instructions according to the example shown in FIG. 2contains, at least in installed condition, firstly instructions 50 forthe data processor system 3 to send to the printer printing instructionswhich define printing to be printed on the sheet-like objects. These areinstructions for actually outputting to the printer printinginstructions that can form, for instance, the output of a printerdriver. In principle, this may be carried out under variouscommunication protocols, which protocols are known per se and aretherefore not discussed further.

[0028] Further, the set of instructions according to this exampleincludes instructions 51 for registering output data concerning theoutput of printing instructions to the printer 2, which registeredoutput data are at least indicative of printer capacity required forcarrying out the printing instructions sent to the printer 2. Printercapacity is herein understood to mean the claim imposed on one or moreportions of the printer 2. According to this example, the claim on theprinter capacity is expressed in terms of the number of pages to beprinted when carrying out the printing instructions sent. This number issimply registered during step 51 by increasing a counter “n” by thevalue “1” each time after instructions for printing a page have beensent to the printer 2. This counter “n” is then set during aninitialization step 52 to a start value “0” at the start of theprocessing of printing instructions for printing a series of printedobjects.

[0029] Furthermore, the program contains instructions for at leastperiodically registering production data in accordance with signalsreceived from the detector, which are at least indicative of a quantityof production realized by the printer 2 in response to the printinginstructions sent to the printer 2. According to this example, theproduction data are formed by numbers of sheets detected by the detector13.

[0030] Furthermore, the computer program contains instructions fordosing the sending of next printing instructions, depending on theproduction data. In particular, the instructions will ensure that, onthe one hand, the amount of instructions in the buffer memory 26 of theprinter 2 remains limited and, on the other hand, that amount is notlimited to such an extent that this essentially limits the productionrate of the printer. Examples thereof will be discussed hereinbelow.

[0031] Incidentally, it is possible to arrange the data processor system3 especially for controlling the system as proposed and then tointegrate it therein as well. This may offer advantages, for instancebecause then the putting into use requires less installation on dataprocessor equipment.

[0032] If a data processor system 3, a printer 2 and an inserter systemare already available, it is sufficient, for the practice of the methoddescribed hereinbelow in more detail, to have a suitably arranged set ofinstructions available in a form readable and processable by a dataprocessor system. Thus the configuration already present can be renderedsuitable for the application of the method proposed.

[0033] The method according to the example shown in FIG. 2 furtherprovides a base cycle, with which the amount of information present inthe buffer memory of the printer can be controlled or at leastinfluenced.

[0034] The registering of sheets printed by the printer 2 is done byreading out the detector 13 (step 54) in a separate reading cycle. Thiscycle is traversed with a frequency so high that the cycle time is lessthan the time that a sheet is minimally detected by the detector. Thisensures detection of each single sheet. By only registering switchesfrom detection-no to detection-yes, double count of sheets is prevented.The reading cycle is also started with the initialization step 53. Thena variable “1” indicating if the process is in a reading mode (duringwhich reading mode the variable “d” must not be changed to preventmissing of counts) is set to “no” and a counter “d”, which updates thenumber of detected sheets, is set to zero.

[0035] The first step 55 of the reading cycle is to determine whetherthe process is in the reading mode. If this is not so, the detector isread out (step 54). Subsequently, it is verified in step 56 whetherthere is a switch from “no” sheet detection to “yes” sheet detection. Ifthis is not so, step 55 is returned to. If a switch from no sheetdetection to sheet detection, is detected, it is concluded that a sheethas arrived at the sensor 13 and in step 57 the value of the variable“d” is increased by “1”.

[0036] During the initialization step 53, also a counter “m”, whichupdates the number of counted sheets, is set to zero.

[0037] From a given moment, the printer prints one of the sheet-likeobjects in response to and in accordance with the printing instructionssent to the printer 2. This step does not take place under directcontrol by the data processor system 3 or the inserter system 1 and istherefore not shown in FIG. 2. Furthermore, this can be carried out withgenerally commercially available printers, so that a discussion thereofis not necessary for the practice of the proposed method.

[0038] Both last-mentioned considerations also hold for the step of eachtime directly delivering each of the sheet-like objects printed by theprinter 2 from the printer 2 to the finishing apparatus formed by theinserter system 1, and this step, too, is not shown as such in FIG. 2.

[0039] The finishing by the inserter system 1 of the sheet-like objectsdelivered by the printer 2 to the finishing apparatus 1 can take placein a conventional manner and is therefore not described or discussed inmore detail.

[0040] Each time, following the step 50 of sending instructions forprinting a sheet and following a “no” result resulting from the step 61of comparing the sent instructions with the realized production, thereading mode is activated by giving the variable “1” the value “yes”(step 58). The next time the reading cycle traverses the step 55 ofdetermining whether the process is in the reading mode, the result ofthat step is “yes”, and as next step 59 the counter “m” is increased bythe current value of “d” representing the number of sheets detectedsince the last time the reading mode was operative. Subsequently, thecounter “d” of the number of sheets detected since the last reading modeis set to zero (step 60). The reading cycle then proceeds to re-read thedetector (step 54).

[0041] After the current data concerning the printing instructions sentto the printer and the realized printing production have been gathered,each time the question becomes relevant whether the instructions forprinting the next sheet should already be sent to the printer 2. Thisquestion is answered by determining whether the difference between thenumber of sheets “n” for which printing instructions have been outputtedto the printer 2 and the number of sheets “m” detected by the detector13 does not exceed a specific maximum “b” (step 61). This maximum “b”has been read just before during a step 62 and has been chosen such thatthe number of sheets “b” for which printing instructions have beenoutputted, but for which the printing and delivery has not yet beencompleted is so large that the speed of the system is not inhibited bythe buffer stock of printing instructions in the printer periodicallygetting empty. If the printer 2 is faster than the inserter system 1, atleast at the employed settings of the inserter system 1, it is notdisadvantageous to accept some speed reduction of the printer, as longas it does not fall below the maximum production rate of the insertersystem at the given settings.

[0042] The reading of the detector and the updating of the counter “d”preferably takes place in a separate processor belonging to thedetector. Communication with the detector is then each time onlynecessary in the reading mode. This is activated with a lower frequencythan the reading out of the detector (step 54).

[0043] Detecting individual sheet-like objects conveyed by the printerand registering output data that are at least indicative of the numberof sheet-like objects to be printed by the printer, as well asregistering the production data by counting numbers of sheet-likeobjects detected by the detector, provides the advantage that thedetection of sheet-like objects is relatively simple and that an exactrelation between the data concerning the number of sheets according tothe registered output data and the number of sheets to be eventuallydetected is relatively simple to realize, in particular if the printeris a Postscript printer which separately receives printing instructionsfor individual pages.

[0044] The production data can form both a direct representation ofthose data and an estimation of those data. A direct representation may,for instance, be the number, scanned by a sensor, of sheet-like objectsdelivered by the printer. An example of an indication of the number ofdelivered sheets is formed by the number of sheets taken up by theprinter. For the detection of delivery of sheets the system according toFIG. 1 is provided with two detectors 27, 28, which can detect deliveryof sheets from the trays A, B. These may, for instance, be microswitchescapable of detecting the passage of a trailing edge of a sheet from therespective tray A, B. The number of sheets taken up by the printer formsa very early indication of the stage of processing of printinginstructions by the printer, which enables a rapid response by supply offurther printing instructions. The average amount of printinginstructions in the buffer memory of the printer may thus be stillsmaller without this leading to regular losses of speed through shortageof printing instructions.

[0045] Because in the practice of the above-described example theregistered output data are repeatedly compared with the registeredproduction data, and the dosing of the output of the next printinginstructions to the printer takes place, at least partly, depending onresults of the comparisons, a direct control of the amount of printinginstructions in the buffer memory 26 of the printer 2 is obtained, sothat this amount can be kept relatively small without this having anessentially adverse effect on the speed of the printer.

[0046] For the direct control of the amount of printing instructions inthe buffer memory 26 of the printer 2 it is further advantageous thatthe results of the comparisons between the registered output data andthe registered production data are compared with a reference value “b”and that the dosing of next ones of the printing instructions takesplace in response to the result of the comparison with the referencevalue “b”.

[0047] The use of a reference value “b” further offers the advantagethat the amount of printing data in the buffer memory of the printer canbe simply increased and decreased by increasing or decreasing thereference value. Thus, by means of measurements of the production rateat different reference values, it can simply be experimentallydetermined what is the smallest reference value at which the systemoperates without essential loss of speed. If desired, some loss of speedmay be accepted if this gives a substantial reduction of the amount ofprinting instructions in the buffer memory of the printer.

[0048] Also when using the same finishing apparatus/printer combination,however, the optimum reference value may vary strongly, for instancedepending on the type of printing instructions (symbols or graphic,bit-map or vector, pre-loaded or not pre-loaded characters, etc.), thevariation in printing and the production rate of the finishing apparatusfeasible at the given setting. In order to be able to choose a favorablevalue of the reference value without experimental measurements, thesetting of the reference value is preferably done automaticallydepending on quantity per unit time of production realized by theprinter.

[0049]FIG. 3 shows an example of a flow diagram for automaticallycontrolling the value reference value “b” depending on the realizedprinting production rate of the printer 2. The control of the referencevalue “b” begins with an initialization step 62. In this step the valueof a counter “w” is set to 1 and “b” obtains a start value. This startvalue can be inputted by hand and, for instance, be expressed in anumber of pages to which the printing instructions relate or in thequality of the printing instructions, for instance in kbytes. The startvalue may also be the value with which the printing and finishing of aprevious series of documents has ended. Preferably, start values for “b”are coupled to so-called “job settings”, so that for each type ofoperation occurring more often, and for which the ideal value of “b”will generally differ little from one time to the next, a matching valueof “b” is set from the beginning of the production, and during theproduction only fine adjustment of the value of “b” will take place.

[0050] Subsequently, within a period of time T_(w) the number of sheetsthat is printed is counted (step 63), and this value is assigned tovariable “v”. The counted value is assigned in a next shift step 64 to avariable “v”. Further, the counter “w” is increased and the value 0.9bis assigned to “b”. The value of “b” is thus reduced. A more or lessaggressively regulatory effect can be obtained by choosing the reductionfactor smaller or greater. Subsequently, during a next period T_(w) thenumber of sheets that is printed is counted again and assigned to thevariable “v” (step 65). Then follows step 66 consisting of thecomparison of “v” and “v_(old)”. If “v” is equal to or greater than“v_(old)”, step 64 is repeated, whereby the value of “b” is againreduced. If “v” is smaller than “v_(old)”, “b” is not reduced further,for the printer has slowed down. The next step is step 67, which isequal to step 64, except that “b” is increased again. Subsequently,during the next period of time T_(w) the number of sheets that isprinted is counted again and assigned to the variable “v” (step 68), andin step 69 the effect of increasing “b” on the speed of the printer 2 isdetermined. If “v” is greater than “v_(old)”, the next step is step 67,whereby “b” is increased again. If this is not the case, the next stepis step 64, i.e., “b” is reduced.

[0051] In steps 66 and 69 other criteria may also be included, such asminimum differences or maximum velocities, for instance resulting fromthe maximum production rate of the finishing apparatus at a givensetting. Also, the extent to which “b” is changed can be made dependenton the difference or the ratio between “v” and “v_(old)”.

[0052] According to the examples described above with reference to FIGS.2 and 3, the output of printing instructions to the printer is each timeinitiated in response to new information concerning the realizedproduction. In situations where the number of sheet-like objects to beprinted forms a less good measure of the required printer capacity, theregistered output data are preferably at least indicative of the amountof printing instructions that have been sent to the printer per unit oftime, in other words: for the rate at which printing data have been sentto the printer. Such a situation occurs, for instance, if the responsetime to a command to output printing instructions to the printer variesstrongly, if the printing instructions per unit to be sent to theprinter (for instance, instructions for a page or for a document) varystrongly as regards data quantity or as regards processing time requiredby the printer, or if the interruption of the print flow is difficult tocarry out. Instead of each time dosing the moment of sending nextinstructions, it is then especially advantageous to dose the amount ofnext printing instructions per unit of time.

[0053] The amount of printing instructions sent to the printer per unitof time may, for instance, be dosed by controlling the duration of theinterval between the output of printing instructions to the printer forprinting successive pages. The initial value of the duration of such aninterval is preferably smaller than the duration of the interval afterwhich the printer changes to a doze mode. The transition of the printerto the doze mode causes an extreme reduction of the average printerspeed, and this may cause artifacts in the response time, as a result ofwhich the regulatory process does not respond by shortening the idletime. In order to prevent dozing of the printer, it is generallydesirable to keep the idle time between the sending of sets of printinginstructions for the printing of successive pages shorter than 10seconds.

[0054] It is also possible, however, to control the rate at whichprinting instructions are sent to the printer in a different manner, forinstance by varying the time between successive bytes. A suitablecontrol range for the duration of the interval between successive bytesmay then be, for instance, 0.5 to 3 milliseconds.

[0055] In combination with the above-described registering of dataconcerning printing instructions sent to the printer and realizedprinting production, the amount of printing instructions per unit oftime can be outputted in response to these data. It is also possible,however, as in the example shown in FIG. 4, to arrange that theproduction data are at least indicative of the quantity per unit of timeof production realized by the printer in response to the printinginstructions sent to the printer, in other words, of the productionrate, for instance expressed in sheets per minute. Dosing the output ofprinting instructions to the printer 2 in response to data that are atleast indicative of the production rate offers the advantage that directfeedback occurs on the basis of the rate which also forms one of theproperties of the process to be optimized.

[0056] This dosing can then be carried out with the intermediate step ofinfluencing the size of the amount of instructions in the buffer memory26 of the printer 2—as according to FIG. 3. However, dosing is alsopossible without monitoring how many printing instructions have beensent but have not yet resulted in printing production. Such a balanceis, for instance, hard to update if the data concerning the detectedproduction concern a different variable than the data concerning theprinting instructions sent to the printer. This is, for instance, thecase if the printing instructions are provided as files in a printerlanguage that does not contain data concerning the number of pages, andthe printing production is detected by detecting and registering thenumber of sheets taken up or delivered by the printer.

[0057] An example of such a manner of dosing the amount of printinginstructions outputted to the printer per unit of time is shown as aflow diagram in FIG. 4. During an initialization step 70 the value 1 isassigned to a counter “w”, and the duration of the time interval “p”between sending successive bytes obtains a value “p_(start)”. The value“p_(start)” may be a standard value or be inputted by hand. Preferably,however, “p_(start)” has a value equal to a value of “p” reached beforein operation, or of an (optionally weighted) average of such values.Just like the value “b” in the examples shorn in FIGS. 2 and 3, thevalue “p” may preferably also be coupled to so-called job instructions,so that previously found values of the duration of the time interval “p”are available—for generally similar printings—are available from thebeginning of the printing and finishing process. An optimum value of “p”is then generally reached sooner than when a more arbitrary value of “p”is started from. Finally, the variable “t” obtains the start value 0,and “t” is started, after which it runs up, controlled by atime-dependent signal.

[0058] Subsequently, printing and finishing are carried out during aperiod of time until a time limit “T_(w)” (step 71). After passing thetime limit “T_(w)” a value equal to the number of sheets counted in theperiod until t=T_(w) is assigned to a variable “v” (step 72).

[0059] Subsequently, as step 73, the duration of the time interval “p”between successive bytes of the printing instructions for a next periodof time is extended by increasing it by a factor of 1/0.9. Here, too, adifferent factor may be chosen depending on the desired speed of thecontrol behavior and the stability. The counter “w” is increased by thevalue 1, and the value “v” is assigned to the variable “v_(old)”.

[0060] Subsequently, during a next period of time until the time limit“T_(w)” (the value “w” has meanwhile been increased) printing andfinishing are carried out (step 74). After reaching the next time limit“T_(w)” a value equal to the number of sheets counted in the perioduntil t=T_(w) is assigned to a variable “v” (step 75).

[0061] After printing has been carried out with two different timeintervals between the successive bytes, it is established by comparing“v” and “v_(old)” whether the extension of the time interval “p” has hada decelerating effect on the printing speed (step 76). If this is notthe case or (depending on the accepted tolerances) is not the case to asubstantial extent, step 73 is returned to, and the value of “p” isincreased again for a next time interval. If during step 76 it isdetermined that the value of “v” has been reduced, step 77 is carriedout as the next step. This is equal to step 74, albeit that the value ofthe time interval “p” between successive bytes of printing instructionsis now reduced instead of increased, and hence the supply of printinginstructions to the printer is accelerated.

[0062] Subsequently, during a next period of time until the time limit“T_(w)” (the value “w” has meanwhile been increased again) printing andfinishing are carried out (step 78). After passing the time limit“T_(w)” a value equal to the number of sheets counted in the perioduntil t=T_(w) is assigned again to a variable “v” (step 79).

[0063] Subsequently, it is determined whether the printing speed hasincreased with respect to the preceding period of time by determiningwhether “v” is greater than “v_(old)” (step 80). If this is not thecase, a reduction of the time between successive bytes proves to yieldno increase in the printing speed, and it is tried again whetherincrease of the time “p” is possible without essentially limiting theprinting speed (steps 73-76). If the printing speed does prove to haveincreased, it is tried once again whether a reduction of the timebetween successive bytes yields an increase in the printing speed (steps77-80). Thus the amount of printing instructions sent to the printer perunit of time is always kept near a value at which a reduction of thatamount begins to have an adverse effect on the production rate.

[0064] If “p” is chosen too small, the memory of the printer fills upjust as in conventional situations, in which the amount of printinginstructions per unit of time outputted to the printer is not dosed. Thelimitation of the amount of printing instructions sent to the printer isthen controlled in a conventional manner. Meanwhile the value of “p” isgradually increased without this affecting the printing speed, until theamount of printing instructions per unit of time sent to the printer hasbeen smaller than the amount the printer can convert to printingproduction for a time so long that the buffer memory 26 of the printer 2begins to become empty to the extent where this begins to affect theprinting speed. In response to that phenomenon the value of “p” isreduced again from cycle to cycle.

[0065] Since printers used for printing large series of postal itemsgenerally require about 5-20 s to gain speed, the time duration of acycle between T_(w) and T_(w+1) is generally preferably from 30-40 s to60-90 s.

[0066] Especially if the rate or the moment of sending printinginstructions is made completely or partly dependent on the productionrate realized by the printer, it is important that the speed of theprinter not be disturbed by phenomena that are not at least expressed inthe registered output data or the registered production data.

[0067] Especially if the quantity of the printing instructions variesstrongly from one sheet-like object to another, it is advantageous ifthe output data contain at least an indication concerning the quantityof the printing instructions sent.

[0068] In addition, the type of printing instructions typically alsoaffects the processing rate of the printer. For instance, graphic imagescost extra time (in relation to the quantity of the printinginstructions), especially when vector representations and color imagesare concerned. If characters are to be printed, the type of characterand the presence thereof in the memory of the printer generally has adecelerating effect on the processing rate. Provisions for improving theresolution and compressed files generally also cost much time.Disturbance of the dosing of the printing instructions due to variationregarding these properties can be prevented by including in theregistered output data at least indications concerning the type ofprinting instructions. Also when detecting production data, dataconcerning the type of realized printing instructions can be registeredfor this purpose.

[0069] An extra reason why it is advantageous to include in theregistered output data at least indications concerning the type ofprinting instructions is that the minimum amount of printinginstructions in the buffer memory of the printer required for attainingthe maximum printing speed can be different for different types ofprinting instructions. Thus, an optimum operation of a raster imageprocessor when processing graphic printing instructions generallyrequires a larger amount of instructions in the buffer memory than whenprocessing printing instructions consisting of signs. Other factors thatfor the purpose of fast processing generally require a relatively largeamount of data in the buffer memory are: the use of resolutionenhancement, vector representation (in comparison with bitmaprepresentation), data compression and color (in comparison withblack-and-white). If it is known that of a specific type of printinginstructions more data are required in the buffer memory to attain theoptimum printer speed, it is therefore advantageous for printinginstructions of that type to be sent to the printer earlier or at ahigher data transmission rate.

[0070] In order to automatically gather information for a printerconcerning the influence of different properties of the printinginstructions or the production data, such as the type of printinginstructions (for instance signs or graphic), the quantity, the numberof pages, numbers of applied signs and the size of the surface of theprinting, it is advantageous if the influence on the processing time ofdifferent properties of the printing instructions or the production datais observed and is processed by multivariate statistic analysis toempirical rules for predicting the processing time starting fromproperties of the printing instructions to be output to the printer.Thus the influence of such properties for a specific type of printer canbe automatically gathered empirically.

[0071] To further limit paper waste in case of a failure occurringdownstream of the printer 2, paper supply blockers 47, 48 are providedat the paper feed of the printer. In response to a message of a failureto the control unit 4 these paper blockers are activated for blockingthe paper feed of the printer 2. Thus the printing of further sheets isprevented and restarting the system is simplified, because fewer sheetsor no sheets at all need to be removed therefrom and because manyprinters are arranged to reprint a sheet after a failure in the papertransport has been detected. The paper blockers simulate such a failurein response to a report on an actual failure in the finishing system 1.The paper blocker may, for instance, be constructed as a pre-stressedclamp released in response to a failure for clamping together the sheetsin the trays A and B, respectively, so that the printer 2 does notsucceed in taking up sheets from the trays. A special advantage of theuse of paper blockers acting on the paper feed of the printer is thatthey are applicable very universally, because no internal interventionin or adaptation to the control of the printer is required and yet avery rapid reaction to failures downstream of the printer can beobtained.

1. A method for printing and finishing sheet-like objects utilizing adata processor system (3), a printer (2) and a finishing apparatus (1),comprising the steps of: the data processor system (3) outputting to theprinter (2) printing instructions defining printings to be printed onthe sheet-like objects; printing said sheet-like objects in responsethereto and in accordance with the printing instructions outputted tothe printer (2); the printer (2) delivering the printed sheet-likeobjects directly to the finishing apparatus (1); and the finishingapparatus (1) finishing the sheet-like objects delivered by the printer(2) to the finishing apparatus (1); characterized by registering outputdata concerning the printing instructions sent to the printer (2), whichregistered output data are at least indicative of printer capacityrequired for the printer (2) to process the printing instructionsoutputted to the printer (2); detecting sheet-like objects displaced bythe printer (2) and generating signals representing detection ofsheet-like objects displaced by the printer (2); at least periodicallyregistering production data in accordance with the signals received fromsaid detector (12, 13, 27, 28), which production data are at leastindicative of a quantity of production realized by the printer (2) inresponse to the printing instructions sent to the printer (2); anddepending on at least said production data, dosing the sending to theprinter (2) of next ones of the printing instructions.
 2. A methodaccording to claim 1, wherein the printing instructions contain printinginstruction sets which each define at least one printing to be printedon at least one of the sheet-like objects, and wherein said dosing isdone by each time controlling moments of sending the printinginstruction sets.
 3. A method according to claim 1 or 2, wherein theregistered output data are at least indicative of the number ofsheet-like objects to be printed by the printer (2) and whereinregistering said production data comprises counting numbers ofsheet-like objects transported by the printer (2).
 4. A method accordingto any one of the preceding claims, wherein the registered output dataare at least indicative of the number of documents to be printed by theprinter (2), wherein at least one of said documents is composed ofseveral of said sheet-like objects, and wherein registering theproduction data comprises detecting documents and counting numbers ofdetected documents.
 5. A method according to any one of the precedingclaims, wherein the registered output data are at least indicative ofthe quantity of the printing instructions outputted to the printer (2).6. A method according to any one of the preceding claims, wherein theregistered output data are at least indicative of the type of theprinting instructions outputted to the printer (2), and wherein types ofprinting instructions requiring relatively much processing time areoutputted to the printer in an accelerated manner.
 7. A method accordingto any one of the preceding claims, wherein the influence on theprocessing time of different properties of the printing instructions orthe production data is observed and is processed through statisticanalysis into empirical rules for predicting the processing timestarting from properties of the printing instructions to be outputted tothe printer (2).
 8. A method according to any one of the precedingclaims, wherein the registered output data are at least indicative ofthe time required for the printer (2) to execute the printinginstructions outputted to the printer (2).
 9. A method according to anyone of the preceding claims, wherein registering production datacomprises scanning printings applied by printer (2) and generatingscanning data in accordance with the scanned printings.
 10. A methodaccording to claim 9, wherein the scanning data obtained by scanningprintings applied by the printer (2) are compared with registered outputdata concerning printing instructions, and wherein printing instructionsare identified as executed if at least a particular extent of agreementbetween at least portions of the scanning data and at least portions ofthe registered output data has been found.
 11. A method according to anyone of the preceding claims, wherein the registered output data are atleast indicative of the amount of printing instructions which have beenoutputted to the printer (2) per unit time.
 12. A method according toclaim 11, wherein the production data are at least indicative of thequantity per unit time of production realized by the printer (2) inresponse to the printing instructions sent to the printer (2).
 13. Amethod according to claims 11 and 12, wherein the value of a variablewhich determines how many printing instructions per unit time areoutputted to the printer (2) is controlled in response to the quantityper unit time of production realized by the printer (2) in response tothe printing instructions sent to the printer (2).
 14. A methodaccording to any one of the preceding claims, further comprising atleast repeatedly comparing the registered output data with theregistered production data, wherein the dosing of the sending of thenext printing instructions to the printer (2) is done, at least partly,depending on results of the comparisons.
 15. A method according to claim14, further comprising: each time comparing the results of thecomparisons with a reference value; and dosing next ones of the printinginstructions in response to the result of the comparison with thereference value.
 16. A method according to claims 12 and 15, furthercomprising setting the reference value depending on quantity per unittime of production realized by the printer (2) in response to theprinting instructions sent to the printer (2).
 17. A method according toclaims 11 and 14, further comprising controlling the value of a variablewhich determines how many printing instructions per unit time areoutputted to the printer (2), in response to the results of thecomparisons of the registered output data with the registered productiondata.
 18. A method according to any one of claims 14-17, wherein theresults of the comparison of the registered output data with theregistered production data are at least indicative of the quantity of asyet unprocessed printing instructions outputted to the printer (2). 19.A method according to any one of claims 14-18, wherein the results ofthe comparison of the registered output data with the registeredproduction data are at least indicative of the number of pages to beprinted according to as yet unprocessed printing instructions outputtedto the printer (2).
 20. A method according to any one of the precedingclaims, wherein detecting production by the printer (2) comprises:detecting transport of the sheet-like objects from a holder to aprinting area of the printer (2).
 21. A method according to any one ofthe preceding claims, wherein in response to a failure in the finishingapparatus (1) downstream of the printer (2), after elimination of thefailure, at least a portion of printing instructions sent to the printer(2) of which the associated printing has already been printed is againoutputted to the printer (2) for again printing at least one sheet-likeobject in accordance with said portion of the printing instructions. 22.A system for finishing sheet-like objects printed by a printer (2),comprising a finishing apparatus (1) having an input for receivingdirectly from the printer (2) sheet-like objects printed by the printer(2), and arranged for finishing the sheet-like objects received from theprinter (2); characterized by a detector (12, 13, 27, 28) for detectingat least sheet-like objects displaced by the printer (2); acommunication port (25) for connecting the detector (12, 13, 27, 28) toa data processor system (3) for signaling to the data processordetection by the detector (12, 13, 27, 28) of at least sheet-likeobjects transported by the printer (2); and a set of instructions in aform readable and processable by the data processor system (3), withinstructions for: the data processor system's (3) outputting to theprinter (2) printing instructions defining printings to be printed onthe sheet-like objects; registering output data concerning the printinginstructions sent to the printer (2), which registered output data areat least indicative of printer capacity required for the printer (2) toprocess the printing instructions outputted to the printer (2); at leastperiodically registering production data in accordance with signalsreceived from said detector (12, 13, 27, 28), which are at leastindicative of a quantity of production realized by the printer (2) inresponse to the printing instructions sent to the printer (2); anddepending on at least said production data, dosing the sending of nextones of the printing instructions to the printer (2).
 23. A systemaccording to claim 22, further comprising said data processor system (3)connected to said communication port (25) for communication with saiddetector (12, 13, 27, 28) and arranged for reading and processing saidinstructions.
 24. A system according to claim 22 or 23, wherein thedetector (13) is arranged for detecting individual sheet-like objectstransported by the printer (2), and wherein the instructions of said setare arranged for registering output data which are at least indicativeof the number of sheet-like objects to be printed by the printer (2) andfor registering said production data by counting numbers of sheet-likeobjects detected by the detector (13).
 25. A system according to any oneof claims 22-24, further comprising an accumulation station (10) foraccumulating sheet-like objects printed by the printer (2) to formdocuments which may each comprise several of said sheet-like objects,wherein the detector (13) is arranged downstream of the accumulationstation (10) for detecting individual documents accumulated by theaccumulation station (10), and the instructions of said set are arrangedfor registering output data which are at least indicative of the numberof documents to be printed by the printer (2), wherein at least one ofsaid documents can comprise several of said sheet-like objects, and forregistering said production data by counting numbers of documentsdetected by the detector (12).
 26. A system according to any one ofclaims 22-25, wherein the detector (12, 13) is arranged for scanningprintings applied by printer (2) and for generating scanning data inaccordance with the scanned printings.
 27. A system according to any oneof claims 22-26, wherein the detector (27, 28) is arranged for detectingdisplacement of sheets from a supply holder (A, B) of a printer (2). 28.A set of instructions in a form readable and processable by a dataprocessor system (3), for dosing supply of printing instructions to aprinter (2) in response to signals received from a detector (12, 13, 27,28) separately from the printer (2), which signals are at leastindicative of a quantity of production realized by the printer (2) inresponse to the printing instructions sent to the printer (2),comprising instructions for: the data processor system's (3) outputtingto the printer (2) printing instructions defining printings to beprinted on the sheet-like objects; registering output data concerningthe printing instructions sent to the printer (2), which registeredoutput data are at least indicative of printer capacity required for theprinter (2) to execute the printing instructions outputted to theprinter (2); at least periodically registering production data inaccordance with signals received from said detector (12, 13, 27, 28),which are at least indicative of a quantity of production realized bythe printer (2) in response to the printing instructions sent to theprinter (2); and depending on said production data, dosing the output ofnext ones of the printing instructions to the printer (2).
 29. A setaccording to claim 28, wherein the instructions for carrying out saiddosing are arranged for distinguishing sets of said printinginstructions for printing at least one sheet-like object and forcarrying out said dosing by each time determining moments of sendingsaid sets of printing instructions.
 30. A set according to claim 28 or29, farther comprising instructions for registering the output data in aform which is at least indicative of the quantity of the printinginstructions outputted to the printer (2).
 31. A set according to anyone of claims 28-30, further comprising instructions for registering theoutput data in a form which is at least indicative of the type of theprinting instructions outputted to the printer (2) and for theaccelerated output to the printer of types of printing instructionsrequiring relatively much processing time.
 32. A set according to anyone of claims 28-31, further comprising instructions for observing theinfluence on the processing time of different properties of the printinginstructions and for processing the observations by statistical analysisinto empirical rules for predicting the processing time starting fromproperties of printing instructions to be outputted to the printer (2).33. A set according to any one of claims 28-32, further comprisinginstructions for registering the output data in a form which is at leastindicative of the time minimally required for said printer (2) toexecute the printing instructions outputted to the printer (2).
 34. Aset according to any one of claims 28-33, further comprisinginstructions for comparing the scanning data obtained by scanningprintings applied by the printer (2) with registered output dataconcerning printing instructions and for identifying printinginstructions as executed if at least a particular extent of agreementbetween at least portions of the scanning data and at least portions ofthe registered output data has been found.
 35. A set according to anyone of claims 28-34, further comprising instructions for registering theoutput data in a form which is at least indicative of an amount ofprinting instructions which has been outputted to the printer (2) perunit time.
 36. A set according to claim 35, further comprisinginstructions for generating the production data in a form which is atleast indicative of a quantity per unit time of production realized bythe printer (2) in response to the printing instructions sent to theprinter (2).
 37. A set according to claim 36, further comprisinginstructions for controlling the value of a variable which determineshow many printing instructions per unit time are outputted to theprinter (2), in response to the quantity per unit time of productionrealized by the printer (2) in response to the printing instructionssent to the printer (2).
 38. A set according to any one of claims 28-37,further comprising instructions for at least repeatedly comparing theregistered output data with the registered production data, and fordosing the output of the next printing instructions to the printer (2),at least partly, depending on results of the comparisons.
 39. A setaccording to claim 36, further comprising instructions for each timecomparing the results of the comparisons with a reference value, and fordosing the output of the next ones of the printing instructions inresponse to the result of the comparison with reference value.
 40. A setaccording to claims 36 and 39, further comprising instructions forsetting the reference value depending on quantity per unit time ofproduction realized by the printer (2) in response to the printinginstructions sent to the printer (2).
 41. A set according to claims 35and 38, further comprising instructions for controlling the value of avariable which determines how many printing instructions per time unitare outputted to the printer (2), in response to variation in theresults of the comparisons of the registered output data with theregistered production data, which results are indicative of the amountof as yet unprocessed ones of the printing instructions sent to theprinter (2).
 42. A set according to any one of claims 38-41, furthercomprising instructions for generating the results of the comparison ofthe registered output data with the registered production data in a formwhich is at least indicative of the quantity of as yet unprocessed onesof the printing instructions outputted to the printer (2).
 43. A setaccording to any one of claims 38-42, further comprising instructionsfor generating the results of the comparisons of the registered outputdata with the registered production data in a form which is at leastindicative of the time which the printer (2) minimally requires forprocessing as yet unprocessed ones of the printing instructionsoutputted to the printer (2).
 44. A set according to any one of claims38-48, further comprising instructions for generating the results of thecomparison of the registered output data with the registered productiondata in a form which is at least indicative of the number of pages to beprinted according to as yet unprocessed ones of the printinginstructions outputted to the printer (2).
 45. A set according to anyone of claims 28-44, further comprising instructions for, in response toa signal representing a failure in the finishing apparatus (1)downstream of the printer (2), after elimination of the failure, againoutputting to the printer (2) at least a portion of printing instructionsets sent to the printer (2) of which the associated printing hasalready been printed, for again printing at least one sheet-like objectin accordance with said portion of the printing instructions.